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From: lriffe@triton.unm.edu (Larry Riffe II)
Newsgroups: comp.windows.x
Subject: Re: Can't build qdss on VAX under Ultrix 4.X
Message-ID: <1990Dec19.173749.25314@ariel.unm.edu>
Date: 19 Dec 90 17:37:49 GMT
References: <71012@bu.edu.bu.edu>
Sender: news@ariel.unm.edu (News supported software)
Organization: University of New Mexico, Albuquerque NM
Lines: 109


Brian,
	There is indeed a problem with the 2 lines you mention, but
	the problem is not with the third variable, its with the second.

	It appears that this is not caused so much by a bug but more
	by changes DEC made to their OS that MIT doesn't know about.

	Follow along and I'll explain:

	In mit/server/ddx/dec/qdss/qdss_io.c we have the following lines:

	if (on != SCREEN_SAVER_ON)
	{
	   lastEventTime = GetTimeInMillis();
	   if (!Vaxstar)
	      *(short *) Qdss.memcsr = UNBLANK | SYNC_ON;
	   else
	      ioctl(fd_qdss, SG_VIDEOON, &Sg);            /* <= ERRORS HERE */
	}
	else
	{
	   if (!Vaxstar)
	      *(short *) Qdss.memcsr = SYNC_ON;
	   else
	      ioctl(fd_qdss, SG_VIDEOOFF, &Sg);           /* <= ERRORS HERE */
	}

	With the errors you mentioned occurring on the lines that are
	pointed to.

	In mit/server/ddx/dec/qdss/libtl/tl.h we have:

#ifdef __STDC__
#define SG_MAPDEVICE  _IOR('g', 9, struct sgmap) /* map device to user */
#define SG_VIDEOON    _IO('g',23)             /* turn on the video */
#define SG_VIDEOOFF   _IO('g',24)             /* turn off the video */
#define SG_CURSORON   _IO('g',25)             /* turn on the cursor */
#define SG_CURSOROFF  _IO('g',26)             /* turn off the cursor */
#else
#define SG_MAPDEVICE  _IOR(g, 9, struct sgmap) /* map device to user */
#define SG_VIDEOON    _IO(g,23)             /* turn on the video */
#define SG_VIDEOOFF   _IO(g,24)             /* turn off the video */
#define SG_CURSORON   _IO(g,25)             /* turn on the cursor */
#define SG_CURSOROFF  _IO(g,26)             /* turn off the cursor */
#endif

	And this is where the problem happens!  The variable __STDC__
	is supposed to be defined as 1 if the C compiler is ANSI C
	compliant!  DEC's is not and thus this defines the second set
	of variables instead of the first set.

	Now _IO is defined in /usr/include/sys/ioctl.h!  And DEC decided
	to change this definition between Ultrix 3.1 and 4.0.  Thus 
	causing the problem your having.  

	Ultrix 3.1 /usr/include/sys/ioctl.h:

		#define _IO(x,y)        (int)(IOC_VOID|('x'<<8)|y)

	And Ultrix 4.0 /usr/include/sys/ioctl.h:

		#define _IO(x,y)        (int)(_IOC_VOID|(x<<8)|y)


	If you notice, there are no ' around the x variable.  So, that
	means we have to define our original variables (the ones from
	/mit/server/ddx/dec/qdss/libtl/tl.h) as if we are using an ANSI
	C compliant compiler.  But, since we are not using an ANSI C
	compliant compiler (I've heard that DEC is working on this,
	but so far, their C compiler is not) we get an error and the
	color X server doesn't build for a VAX arch. machine.

	So, the question is how to fix this.  I've come up with two 
	methods, the first I don't know how to implement and the second
	which is a hack but does happen to work.

	The first method involves modifying the imakefile so that it
	will compile all of the source code in mit/server/ddx/dec/qdss
	with the option -DOSMajorVersion=???.  Then change the #ifdef
	in mit/server/ddx/dec/qdss/libtl/tl.h to look like:

	#if ( (__STDC__) || ( OSMajorVersion > 3 ) )

	The only problem with this, is that I don't know how to modify
	the imakefile to compile everything with the option I specified
	above!  Is there anybody out there who can tell me what needs
	to be changed to do this?

	The second method is a hack, I don't like it, but it's quick
	and it works.  The first thing is to make a backup copy of
	mit/server/ddx/dec/qdss/libtl/tl.h.  Then edit the copy in
	your source tree so that there is no longer a #ifdef and you
	only define the correct variables.  i.e.

#define SG_MAPDEVICE  _IOR('g', 9, struct sgmap) /* map device to user */
#define SG_VIDEOON    _IO('g',23)             /* turn on the video */
#define SG_VIDEOOFF   _IO('g',24)             /* turn off the video */
#define SG_CURSORON   _IO('g',25)             /* turn on the cursor */
#define SG_CURSOROFF  _IO('g',26)             /* turn off the cursor */

	Make sure you keep a backup copy of this file so that you can
	put it back in place after you have compiled the server code.

					Hope this helps,

						Larry G. Riffe II
						lriffe@triton.unm.edu
						lriffe@triton.cirt.unm.edu